Low-pressure turbine

ABSTRACT

A double-flow low-pressure partial turbine is provided herein, wherein the exhaust steam of the first flow and the exhaust steam of the second flow are deflected in a common direction within the outer housing and thus axial outlet flow occurs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2013/065466 filed Jul. 23, 2013, and claims the benefitthereof. The International Application claims the benefit of EuropeanApplication No. EP12178221 filed Jul. 27, 2012. All of the applicationsare incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a low-pressure turbine comprising a first flowand a second flow and also a rotor and an inner housing arranged aroundthe rotor and an outer housing arranged around the inner housing. Theinvention also relates to a method for operating a low-pressure partialturbine, the low-pressure partial turbine having a double-flowconfiguration.

BACKGROUND OF INVENTION

Steam turbines are usually divided into partial turbines. Thus, by wayof example, a steam turbine used in local power supply is divided into ahigh-pressure partial turbine, an intermediate-pressure partial turbineand a low-pressure partial turbine. Each of these individual partialturbines mentioned above is accommodated in each case in an individualhousing. Moreover, designs in which the high-pressure part and theintermediate-pressure part are accommodated in a common housing areknown. Designs in which the intermediate-pressure part and thelow-pressure part are arranged in a common housing are similarly known.An axial arrangement of the individual partial turbines in successionrequires a comparatively large amount of installation space.

Since, for reasons of thermodynamics, the pressure and the temperatureof the steam decrease from the high-pressure partial turbine to thelow-pressure partial turbine, and as a result the volume increasesgreatly, in some cases a plurality of partial turbines are used.Moreover, the low-pressure partial turbines generally have a two-flowconfiguration. This means that the inflowing steam flows away both inone direction and also axially in the opposite direction. Low-pressurepartial turbines are configured in such a manner that the exhaust steamin one flow and the exhaust steam in the second flow are carried awaylaterally. This is also known under the term Single Side Exhaust orDouble Side Exhaust. A further embodiment provides that the low-pressureexhaust steam is carried away downward (what is termed Down Exhaust).This generally leads to an increased space requirement, sincelow-pressure partial turbines configured in this way have to beconstructed either with a great width or with a great height. Inparticular, in the case of a Single Side Exhaust assembly, the pipesystem is concentrated on one side, and might therefore lead to problemsin terms of space. It would be desirable to have a narrow machinehousing, in which the partial turbines can be arranged. Moreover, it isdesirable to be able to implement a well-structured pipe system.

SUMMARY OF INVENTION

It is an object of the invention to specify a low-pressure partialturbine which requires relatively little space.

This object is achieved by a low-pressure partial turbine as claimed inthe independent claim.

Advantageous developments are specified in the dependent claims.

An embodiment of the invention proceeds from the aspect that guidance ofthe low-pressure exhaust steam laterally or downward results in a highspace requirement, and this can be eliminated by guiding thelow-pressure exhaust steam in such a manner that it is carried awayaxially. To this end, it is proposed according to an embodiment of theinvention to design the outer housing in such a manner that the exhauststeam chamber of the second flow is designed in such a manner that thesteam is deflected in the same direction as the exhaust steam of thefirst flow. This means that the low-pressure exhaust steam of the secondflow is deflected in the direction of the low-pressure exhaust steam ofthe first flow.

Advantageously, an annular space is thus formed between the innerhousing and the outer housing, a low-pressure exhaust steam of thesecond flow flowing through said annular chamber and mixing with thelow-pressure exhaust steam of the first flow on the output side.

An alternative embodiment would be a box-like construction of the innerhousing outer wall, such that the inner housing could be positioned onthe base in the thus formed chamber.

It is thus proposed according to an aspect of the invention to design anew outer housing for a two-flow low-pressure partial turbine whichmakes an axial discharge flow possible. The machine housing costs canthereby be reduced. Moreover, it is thereby possible to harmonize thebasic power plants. Accordingly, considerable cost savings are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention will be explained in more detail on the basisof an exemplary embodiment.

The FIGURE shows a schematic cross-sectional view of a low pressurepartial turbine.

DETAILED DESCRIPTION OF INVENTION

The FIGURE shows a low-pressure partial turbine 1, which has a two-flowconfiguration. This means that the low-pressure partial turbine 1 has afirst flow 2 and a second flow 3. Live steam flows into the low-pressurepartial turbine 1 via an admission connector 4. A flow path 8 is formedbetween a rotor 6 mounted rotatably about an axis of rotation 5 and aninner housing 7 arranged around the rotor 6.

An outer housing 9 is arranged around the inner housing 7. The rotor 6is formed with individual rotor blades 10. For the sake of clarity, onlyone rotor blade is provided with the reference sign 10. Guide vanes 11arranged on the inner housing 7 are arranged between the individualrotor blade stages. For reasons of clarity, only one guide vane isprovided with the reference sign 11.

Live steam flows in via the admission connector 4 and is expanded in thefirst flow 2 to the right, as seen in the plane of the drawing, and inthe second flow 3 to the left, as seen in the plane of the drawing. Thesteam is expanded in the flow path 8 and is cooled in the process. Afterthe last rotor blade 10 and guide vane 11, the low-pressure exhauststeam 12 is deflected in the second flow 3 through the inner housing 7.For this purpose, the outer housing 9 has deflection elements 13, whichdeflect the steam again in the axial direction to the first flow 2. Anannular space 14, through which the low-pressure exhaust steam 12 of thesecond flow 3 flows, is formed between the outer housing 9 and the innerhousing 7. The low-pressure exhaust steam 16 of the first flow 2 ismixed with the low-pressure exhaust steam of the second flow 12 in amixing zone 15. In this respect, it has to be ensured that the velocityof the low-pressure exhaust steam 16 of the first flow 2 issubstantially the same as the velocity of the low-pressure exhaust steam12 of the second flow 3 in the mixing zone 15.

Then, the steam mixed from the low-pressure exhaust steam 16 of thefirst flow 2 and the low-pressure exhaust steam 12 of the second flow 3flows into an exhaust steam chamber 17 and, after this exhaust steamchamber 17, to the condenser (not shown in more detail). A base for abearing 18, on which the rotor 6 is mounted, is arranged in the exhauststeam chamber 17. The site of the bearing 18 can be arranged in thesteam chamber or, in alternative embodiments, can be positioned as aseparate encapsulated base outside the steam chamber.

The low-pressure partial turbine (1) has a double-flow configuration andthe exhaust steam from the first flow (2) is deflected in the directionof the exhaust steam of the second flow (3). The direction of theexhaust steam from the first flow (2) and the direction of the exhauststeam from the second flow (3) are oriented substantially parallel tothe axis of rotation (5).

1. A low-pressure partial turbine, comprising a first flow and a secondflow, a rotor mounted rotatably about an axis of rotation, an innerhousing arranged around the rotor and an outer housing arranged aroundthe inner housing, wherein the low-pressure partial turbine is designedin such a manner that exhaust steam from the first flow which flowsduring operation through the low-pressure partial turbine flowssubstantially in the same direction as the exhaust steam from the secondflow, wherein the low-pressure partial turbine has a double-flowconfiguration and the exhaust steam from the first flow is deflected inthe direction of the exhaust steam of the second flow, and wherein thedirection of the exhaust steam from the first flow and the direction ofthe exhaust steam from the second flow are oriented substantiallyparallel to the axis of rotation.
 2. The low-pressure partial turbine asclaimed in claim 1, wherein the outer housing comprises a return steamchamber for returning the steam to the exhaust steam chamber of thesecond flow.
 3. The low-pressure partial turbine as claimed in claim 1,further comprising an annular chamber, which is arranged between theinner housing and the outer housing.
 4. The low-pressure partial turbineas claimed in claim 1, wherein the deflection is effected in the outerhousing.
 5. The low-pressure partial turbine as claimed in claim 1,wherein the exhaust steam from the first flow and the second flowcondenses in a condenser.